In contrast to the running gags on the “Pigs In Space” vignettes on The Muppet Show, problems associated with Bugs In Space are no laughing matter.
Immunobiologist Ty Lebsack et. al., from the University of Arizona‘s department of Immunobiology in the College of Medicine., have just published “Microarray Analysis of Spaceflown Murine Thymus Tissue Reveals Changes Gene Expression Regulating Stress and Glucocorticoid Receptors” in the 15 May 2010 edition of Journal of Cellular Biochemistry (110:372-381 2010). They flew four healthy mice aboard NASA’s STS-118 Endeavour mission to the International Space Station in September 2007. The mice spent 13 days aboard the Space Shuttle. The researchers compared the gene-expression patterns in thymuses of the four space mice to those from an equal number of control mice on the ground.
“The altered genes we observed were found to primarily affect signaling molecules that play roles in programmed cell death and regulate how the body responds to stress,” Lebsack said.
The down-regulation of proteins regulating cell death has implications for the body of astronauts to combat infections. The decrease in the body’s ability to push infected cells into apoptosis means that astronauts would be more susceptible to infections. Further, based on previously released studies, which indicate that bacteria in space become more virulent, space places a double whammy on astronauts: their immune system becomes less efficient and invading bacteria become more sinister.
In Part II of NASA – ISS Science Success, we noted the Microbe experiments conducted during the STS-115/12A mission to the ISS concerning differential gene expression leading to increased virulence, from NASA’s report on “International Space Station Science Research Accomplishments During the Assembly Years: An Analysis of Results from 2000-2008″ (p 97-98).
Two other reports in the NASA report on ISS science bear on these issues:
Commercial Biomedical Testing Module (CBTM): Effects of Osteoprotegerin (OPG) on Bone Maintenance in Microgravity (Principal Investigator(s): Ted Bateman, Clemson University, Clemson, S.C. on Expedition 4 – Research Area Physiological Studies: Bone and Muscle (p 120).
Data obtained from the mice following return to Earth also indicated some alternations in immune functions. Analysis of the spleenocytes (immune cells produced by the spleen) indicated an increase in B-cell (a white blood cell that matures in the bone marrow and, when stimulated by an antigen, differentiates into plasma cells) production compared to T-cells (white blood cells that complete maturation in the thymus and have various roles in the immune system). A slightly lower white blood-cell count in the flight animals compared to the controls was not statistically significant. The spleen mass was 18% to 28% lower in flight mice compared to controls. Results also indicate that flight mice weighed 10% to 12% less than ground controls (Pecaut et al. 2003).
and the second article, where the experiments were flown on the same STS-118 mission from which Lebsack et. al. obtained their results :
Commercial Biomedical Testing Module-2 (CBTM-2) (Principal Investigator(s): H.Q. Han, M.D., Ph.D., Amgen Research, Thousand Oaks, Calif.
David Lacey, M.D., Amgen Research, Thousand Oaks, Calif. on Expedition 15. (p122-123)
CBTM-2 examined the effectiveness of an experimental therapeutic in preventing muscle loss in mice that were exposed to microgravity.
Certain T- and B-cell counts from the spleens of the flight animals were also low, and the natural killer cells were increased. Analysis of cancer-related genes in the thymus from the flight animals showed that 30 out of 84 genes were expressed differently after flight.
These results were published here: Gridley DS, Slater JM, Luo-Owen X, Rizvi A, Chapes SK, Stodieck LS, Ferguson VL, Pecaut MJ. Spaceflight effects on T lymphocyte distribution, function and gene expression. J Appl Physiol. 2008 Nov 6.
Overall, the results indicate that long term space flight poses two serious problems for astronauts: their immune system becomes less capable under microgravity; and the bugs become more capable.
These problems will need to be resolved before humanity ventures very far into the Solar System.